List which passwords used which log-ins.

You can search for passwords or a subset of a password within the desktop app. Just enter the password or part of a password in the search input field and press enter - all items that have a somehow matching password will be listed.

What you can do to improve your password strength in general is this: Click on the Watchtower icon in the desktop app, then click on the colored bar to get a list of all your items sorted by password strength.

You seem to ignore a strength of a password manager: to establish a different randomized password for every login, no matter how trivial the account. Since it's only one click to fill a password saved in 1Password, it doesn't matter if 1Password fills a trivial or a complex password, so go through all your accounts once and change every reused or trivial password to a generated password. You might thing it's not relevant if an account of a not sensitive login is compromised, however your perception of what is sensitive and what is not might change. If something suddenly becomes sensitive, you need to act immediately and change passwords. But you are always on the safe and convenient side to have just everything at high quality complex randomly generated passwords and never have to evaluate how important one login is.
I once had the same not very complex password for my "unimportant" sites, but this turned out to be dangerous, so I spent one evening about 15 years ago and changed literally all of my accounts to generated passwords.